Control system, control device, conversion device, method for controlling control system, method for controlling control device, and method for controlling conversion device

ABSTRACT

A control system includes a to-be-controlled apparatus disposed in a clean room, a control device disposed outside the clean room and controlling the to-be-controlled apparatus through Ethernet communication, and a conversion device disposed in the clean room and mutually converting communication data on Ethernet communication with the control device and communication data on serial communication with the to-be-controlled apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-210392 filed on Oct. 31, 2017. The entire contentsof this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a control system, a control device, aconversion device, a method to control a control system, a method tocontrol a control device, and a method to control a conversion device.

2. Description of the Related Art

In a facility such as a factory, a transfer system is used in which acarrier traveling on a ceiling, a floor, or the like between a pluralityof processing devices delivers and receives articles. Such a carrierreceives control information from a control device of the transfersystem and travels and operates in accordance with the controlinformation thus received. The transfer system is installed in, forexample, a clean room and is used in a process of manufacturingsemiconductors as articles.

Existing carriers have been in operation in factories for more than tenyears and still use serial communication such as legacy deviceinterfaces (Recommended Standard 232 version C (RS-232C)) to receivecontrol information. A transmission distance of serial communicationconforming to RS-232C that is one of the communication standards ofthese legacy device interfaces is restricted to a range from severalmeters to a few dozen meters. Therefore, when a transfer system isdisposed in a clean room, a control device that controls a carrier viaserial communication is also disposed in the clean room at present.

Japanese Unexamined Patent Application Publication 2011-22974 disclosesa technique for shortening a waiting time from generation of a transfercommand to allocation of the transfer command in a carrier system thatcontrols a carrier traveling in a clean room.

The larger a volume of the clean room is, the more facilities arerequired to maintain cleanliness, which increases demands forsuppressing a maintenance cost of the clean room. There are also demandsfor disposing, outside the clean room, a computer defining andfunctioning as a control device that is not directly involved inmanufacture or transfer of articles, a desk on which the computer isplaced, a chair where a person operating the computer sits, and thelike.

SUMMARY OF THE INVENTION

According to preferred embodiments of the present invention, amaintenance cost of a clean room is reduced.

A control system according to a preferred embodiment of the presentinvention is a control system that causes a control device included in atransfer system to control a conversion device and a to-be-controlledapparatus, the conversion device being controlled via Ethernetcommunication with the control device, the to-be-controlled apparatusbeing controlled via serial communication with the conversion device.The to-be-controlled apparatus is disposed in a clean room. The controldevice is disposed outside the clean room and controls theto-be-controlled apparatus through Ethernet communication. Theconversion device is disposed in the clean room and mutually convertscommunication data on Ethernet communication with the control device andcommunication data on serial communication with the to-be-controlledapparatus.

Accordingly, in the control system, the conversion device is disposed inthe clean room, which eliminates the restriction that a computerdefining and functioning as the control device needs to be disposed inthe clean room and allows the control device to be disposed outside theclean room. When a space occupied by the conversion device is smallerthan that of the control device, a space occupied by the devices of thecontrol system and furniture on which the devices are disposed in theclean room is able to be reduced, which leads to savings in the spaceoccupied by the devices in the clean room. As a result, a maintenancecost of the clean room is able to be reduced.

Further, the control system may include a plurality of the conversiondevices that perform serial communication with a plurality of theto-be-controlled apparatuses on a one-to-one basis. The control devicemay include one Ethernet interface and a plurality of controllersconfigured or programmed to perform Ethernet communication with theplurality of conversion devices on a one-to-one basis via the oneEthernet interface.

According to this configuration, in the control system the controldevice is able to transmit control data to the plurality ofto-be-controlled apparatuses via the plurality of conversion devicesusing the one Ethernet interface. With the control system, a number ofthe control devices is able to be reduced as compared with aconfiguration where the number of control devices is equal to a numberof the to-be-controlled apparatuses. Further, a number of interfaceswhich the control device includes is able to be reduced as compared witha configuration where the control device includes a number of Ethernetinterfaces or legacy device interfaces (for example, serialcommunication interfaces) equal to the number of the to-be-controlledapparatuses.

Further, the conversion device may include a buffer that temporarilyholds the control data received from the control device until thecontrol data is transmitted to the to-be-controlled apparatus. Thecontrol device may be configured or programmed to include an estimatorthat estimates consumption of the buffer, a generator that generatescontrol data to control the to-be-controlled apparatus and transmit thecontrol data which is generated, and a first limiter that determines amaximum transmission rate of the control data based on the consumptionestimated by the estimator and limit a transmission data rate of thecontrol data to be transmitted by the generator to a rate equal to orless than the maximum transmission rate which is determined.

According to this configuration, in the control system, the consumptionof the buffer of the conversion device in the control system isestimated and then the transmission data rate of the control data to betransmitted by the control device is limited in accordance with theestimation. As a result, the control data is able to be delivered to theto-be-controlled apparatus with the buffer of the conversion deviceprevented from overflowing or becoming empty.

Further, the conversion device may include a buffer that temporarilyholds the control data received from the control device until thecontrol data is transmitted to the to-be-controlled apparatus, anacquirer that acquires consumption of the buffer, and a transmitter thattransmits first information indicating that the consumption acquired bythe acquirer is greater than a first threshold to the control device.The control device may include a generator that generates the controldata to control the to-be-controlled apparatus and transmit the controldata which is generated, and a second limiter that sets a maximumtransmission rate of the control data to a value greater than atransmission speed of serial communication between the conversion deviceand the to-be-controlled apparatus. The second limiter may also changethe maximum transmission rate to zero upon receiving the firstinformation from the transmitter.

Accordingly, when a probability that the buffer will overflow based onthe consumption of the buffer of the conversion device increases, thetransmission data rate of the control data to be transmitted by thecontrol device is reduced even in response to a command from theconversion device, which makes it possible to further reduce theprobability that the buffer will overflow based on respectivedeterminations made by both the devices.

The transmitter may also transmit, to the control device, secondinformation indicating that the consumption acquired by the acquirer isless than a second threshold after transmitting the first information.The second limiter may also change the maximum transmission rate to avalue greater than the transmission speed of serial communicationbetween the conversion device and the to-be-controlled apparatus uponreceiving the second information from the transmitter with the maximumtransmission rate set to zero.

Accordingly, when a probability that the buffer will become empty basedon the consumption of the buffer of the conversion device increases, thetransmission data rate of the control data to be transmitted by thecontrol device is increased, which makes it possible to reduce theprobability that the buffer will become empty.

Further, a control device according to a preferred embodiment of thepresent invention controls a to-be-controlled apparatus via conversionbetween Ethernet communication and serial communication performed by aconversion device. The conversion device includes a buffer thattemporarily holds control data received from the control device untilthe control data is transmitted to the to-be-controlled apparatus. Thecontrol device includes an estimator that estimates consumption of thebuffer, a generator that generates the control data to control theto-be-controlled apparatus and transmits the control data which isgenerated, and a limiter that determines a maximum transmission rate ofthe control data based on the consumption estimated by the estimator andregulates a transmission data rate of the control data to be transmittedby the generator to a rate equal to or less than the maximumtransmission rate which is determined.

Accordingly, the same advantageous effects as the control systemdescribed above are obtained.

Further, a conversion device according to a preferred embodiment of thepresent invention is a conversion device that mutually converts Ethernetcommunication performed by a control device and serial communicationperformed by a to-be-controlled apparatus. The conversion deviceincludes a buffer that temporarily holds control data received from thecontrol device until the control data is transmitted to theto-be-controlled apparatus, and a transmitter that transmits, to thecontrol device, first information indicating that consumption of thebuffer is greater than a first threshold to change a maximumtransmission rate of the control data to be transmitted by the controldevice to zero.

Accordingly, the same advantageous effects as the control systemdescribed above are obtained.

Further, a method to control a control system according to a preferredembodiment of the present invention controls a control system thatcauses a control device included in a transfer system to control aconversion device and a to-be-controlled apparatus, the conversiondevice being controlled via Ethernet communication with the controldevice, the to-be-controlled apparatus being controlled via serialcommunication with the conversion device. The method to control thecontrol system includes a control step of causing the control devicedisposed outside a clean room to control the to-be-controlled apparatusdisposed in the clean room through Ethernet communication, and aconversion step of causing a conversion device disposed in the cleanroom to mutually convert communication data on Ethernet communicationwith the control device and communication data on serial communicationwith the to-be-controlled apparatus.

Accordingly, the same advantageous effects as the control systemdescribed above are obtained.

Further, a method to control a control device according to a preferredembodiment of the present invention controls a control device thatcontrols a to-be-controlled apparatus via conversion between Ethernetcommunication and serial communication performed by a conversion device.The conversion device includes a buffer that temporarily holds controldata received from the control device until the control data istransmitted to the to-be-controlled apparatus. The method to control thecontrol device includes an estimation step of estimating consumption ofthe buffer, a generation step of generating the control data to controlthe to-be-controlled apparatus and transmitting the control data whichis generated, and a limitation step of determining a maximumtransmission rate of the control data based on the consumption estimatedin the estimation step and regulating a transmission data rate of thecontrol data to be transmitted in the generation step to the maximumtransmission rate which is determined.

Accordingly, the same advantageous effects as the control systemdescribed above are obtained.

Further, a method to control a conversion device according to apreferred embodiment of the present invention controls a conversiondevice that mutually converts Ethernet communication performed by acontrol device and serial communication performed by a to-be-controlledapparatus. The method to control the conversion device includes anacquisition step of acquiring consumption of a buffer that temporarilyholds control data received from the control device until the controldata is transmitted to the to-be-controlled apparatus, and atransmission step of transmitting, to the control device, firstinformation indicating that the consumption is greater than a firstthreshold to change a maximum transmission rate of the control data tobe transmitted by the control device to zero.

Accordingly, the same advantageous effects as the control systemdescribed above are obtained.

Note that preferred embodiments of the present invention can be embodiednot only as a device but also as a method in which processors of thedevice serve as steps, as a program that causes a computer to executethe steps, as a computer readable recording medium such as a CD-ROM inwhich the program is stored, or as information, data, or signalscorresponding to the program. The program, information, data, andsignals may be distributed over a communication network such as theInternet.

According to the control systems of preferred embodiments of the presentinvention, the maintenance cost of the clean room is able to be reduced.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiment withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a controlsystem according to a preferred embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an existingcontrol system.

FIG. 3 is a block diagram illustrating a first example of a specificconfiguration of a control device according to a preferred embodiment ofthe present invention.

FIG. 4 is a block diagram illustrating a second example of a specificconfiguration of a control device according to a preferred embodiment ofthe present invention.

FIG. 5 is a block diagram illustrating a third example of a specificconfiguration of a control device according to a preferred embodiment ofthe present invention.

FIG. 6 is a block diagram illustrating a fourth example of a specificconfiguration of a control device according to a preferred embodiment ofthe present invention.

FIG. 7 is a block diagram illustrating a functional configuration of acontrol system according to a preferred embodiment of the presentinvention.

FIG. 8 is a flowchart illustrating processing of a control deviceaccording to a preferred embodiment of the present invention.

FIG. 9 is a flowchart illustrating processing for changing an operationmode of a control device according to a preferred embodiment of thepresent invention.

FIG. 10 is a flowchart illustrating processing of a conversion deviceaccording to a preferred embodiment of the present invention.

FIG. 11 is a sequence diagram illustrating an operation example of acontrol system according to a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the drawings.

The preferred embodiments to be described below corresponds topreferable specific examples of the present invention. Numerical values,shapes, materials, elements, placement positions and connection modes ofthe elements, steps, order of the steps, and the like described in thefollowing preferred embodiments are merely examples and are not intendedto limit the present invention. Among the elements in the followingpreferred embodiments, elements not set forth in the independent claimsindicating the top level concept of the present invention will bedescribed as optional elements that relate to a more preferablepreferred embodiment.

Note that the same elements are denoted by the same reference numerals,and the description thereof may be omitted.

In a present preferred embodiment of the present invention, a controlsystem and the like that achieve reductions in maintenance costs of aclean room will be described.

First, a configuration of the control system according to the presentpreferred embodiment will be described based on comparison with acontrol system according to the related art.

FIG. 1 is a block diagram illustrating a configuration of a controlsystem 1 according to the present preferred embodiment.

As illustrated in FIG. 1, the control system 1 includes a main controldevice M, a control device 10, conversion devices 20A and 20B, andto-be-controlled apparatuses 30A and 30B. The main control device M andthe control device 10 are disposed outside a clean room R. Theconversion devices 20A and 20B, and the to-be-controlled apparatuses 30Aand 30B are disposed in the clean room R.

The control system 1 is a control system that controls a transfer systemS. More specifically, the control system 1 controls the to-be-controlledapparatuses 30A and 30B, and the like included in the transfer system Sto cause the transfer system S to transfer articles or to performprocessing on the articles, and the like. Herein, the transfer system Sis a transfer system disposed in the clean room R and is specifically,for example, a transfer system used in a semiconductor manufacturingprocess.

The clean room R is a space with less particulates in air than spaces inthe natural environment, that is, a space with a higher degree ofcleanliness. For example, the space has cleanliness of any one ofcleanliness classes 1 to 9 prescribed in ISO 14644-1.

The main control device M preferably is a computer that manages anentire semiconductor production facility in the clean room R andcontrols the transfer system S. The main control device M generates acontrol command to control the transfer system S and transmits thecontrol command thus generated to the control device 10.

The control device 10 preferably is a computer that controls theto-be-controlled apparatuses 30A and 30B through Ethernet communicationso as to control the transfer system S in accordance with the controlcommand received from the main control device M. More specifically, thecontrol device 10 determines a specific operation to be performed by theto-be-controlled apparatuses 30A and 30B so that the transfer system Soperates in accordance with a transfer plan of articles received fromthe main control device M. Then, the control device 10 generates controldata for the operation and transmits the control data thus generated toa network N by Ethernet communication. For example, the control device10 sets the control data as a payload of an Internet Protocol (IP)packet, that is, encapsulates the control data in the IP packet, andtransmits, by Ethernet communication, the control data. A destination ofthe control data to be transmitted is the conversion device 20A when acontrol target is the to-be-controlled apparatus 30A and is theconversion device 20B when the control target is the to-be-controlledapparatus 30B. Note that the control data may be broadcast from thecontrol device 10. The control device 10 can be configured with hardwareand circuitry such as a personal computer (PC).

The conversion device 20A is a conversion device that mutually convertscommunication data on Ethernet communication and communication data onserial communication. The conversion device 20A is connected to thecontrol device 10 via the network N and is connected to theto-be-controlled apparatus 30A via a serial cable CA. When receiving thecontrol data transmitted by the control device 10 via the network N, theconversion device 20A converts the control data thus received into aserial communication format and transmits the control data thusconverted to the to-be-controlled apparatus 30A. When the control dataencapsulated in an IP packet is transmitted, the conversion device 20Aextracts the control data from the IP packet, that is, decapsulates thecontrol data and performs the above-described conversion. Further, whenreceiving response data transmitted by the to-be-controlled apparatus30A via the serial cable CA, the conversion device 20A converts theresponse data thus received into an Ethernet communication format andtransmits the response data thus converted to the control device 10.

Note that the conversion device 20A is described as a conversion devicethat mutually converts communication data on Ethernet communication andcommunication data on serial communication in the control system 1according to the present preferred embodiment, but the conversion device20A is applicable not only to serial communication but also tocommunication standards belonging to legacy device interfaces (forexample, parallel communication).

An information processing throughput performed by the conversion device20A is lower than an information processing throughput performed by thecontrol device 10, so that the conversion device 20A can be realized asa device that is smaller in size than the control device 10. Forexample, assuming that the control device 10 is configured with adesktop PC, a monitor, a mouse, and a keyboard, the conversion device20A can be configured with, for example, a small PC, a so-called box PCor a mini PC.

The conversion device 20A preferably is such a small PC or the like, sothat the conversion device 20A is able to be attached to a housing ofthe to-be-controlled apparatus 30A and thus eliminates the need forfurniture or the like on which the conversion device 20A is installed inthe clean room R.

The conversion device 20B is a conversion device that is similar incapability to the conversion device 20A. The conversion device 20B isconnected to the control device 10 via the network N and is connected tothe to-be-controlled apparatus 30B via a serial cable CB. The conversiondevice 20B converts control data and response data exchanged between thecontrol device 10 and the to-be-controlled apparatus 30B and transmitsand receives the data thus converted in the same manner as theconversion device 20A.

The to-be-controlled apparatus 30A is an apparatus that is controlledvia serial communication, transfers articles (including containers suchas a front-opening unified pod (FOUP) and a POD containing semiconductorwafers) in the transfer system S and performs processing on thearticles. The to-be-controlled apparatus 30A is a device that controlsan unmanned overhead carrier traveling along a track suspended from aceiling of the clean room R or an unmanned carrier traveling along atrack on a floor of the clean room R. The to-be-controlled apparatus 30Amay be configured or programmed to define a processor that appliesvarious physical or chemical treatments to semiconductor wafers. Theto-be-controlled apparatus 30A operates under control of the controldevice 10. The to-be-controlled apparatus 30A is connected to thecontrol device 10 via the serial cable CA. The to-be-controlledapparatus 30A receives control data transmitted from the control device10 and converted into communication data on serial communication by theconversion device 20A, and operates in accordance with to the controldata thus received.

The to-be-controlled apparatus 30B is an apparatus that is similar incapability to the to-be-controlled apparatus 30A. The to-be-controlledapparatus 30B is connected to the conversion device 20B via the serialcable CB and operates under control of the control device 10.

The network N preferably is a network conforming to the Ethernetcommunication standard. More specifically, the network N is configuredwith a twisted pair cable used for the Ethernet communication standardsuch as 10/100/1000 BASE-T and a communication apparatus (notillustrated) such as a repeater, an Ethernet hub or a router. Although amaximum distance which one twisted pair cable can carry communication isregulated to 100 meters, establishing connection using theabove-described communication apparatus enables communication with aremote location separated by 100 meters or more.

The serial cable CA connects the conversion device 20A and theto-be-controlled apparatus 30A so that serial communication is possible.The serial communication standard is, for example, RS-232C or RS-485. Atransmission distance of the serial cable CA is much shorter than atransmission distance of the network N. Therefore, it is convenient forthe conversion device 20A connected to the to-be-controlled apparatus30A via the serial cable CA or the like to be disposed in the clean roomR where a physical distance from the to-be-controlled apparatus 30A isrelatively short. The above description of the serial cable CA alsoapplies to the serial cable CB.

Note that a description has been given herein of a configuration wherethe control system 1 includes two conversion devices and twoto-be-controlled apparatuses; however, the control system 1 may includethree or more of conversion devices and to-be-controlled apparatuses,for example, several tens or hundreds of conversion devices andto-be-controlled apparatuses. Further, a plurality of control devices 10may be connected under one main control device M, or the main controldevice M and the control device 10 may be both directly connected to thenetwork N.

FIG. 2 is a block diagram illustrating a configuration of an existingcontrol system 100. The existing control system 100 is a control systemdesigned to perform control similar to that of the control system 1without using the conversion devices 20A and 20B illustrated in FIG. 1.

As illustrated in FIG. 2, the control system 100 includes a main controldevice M, control devices 110A and 110B, and to-be-controlledapparatuses 30A and 30B. The main control device M is disposed outside aclean room R, and the control devices 110A and 110B and theto-be-controlled apparatuses 30A and 30B are disposed in the clean roomR. Note that the same reference numerals are given to the same elementsas those illustrated in FIG. 1, and detailed descriptions thereof willbe omitted.

The control system 100 differs from the control system 1 illustrated inFIG. 1 in that the control system 100 does not include the conversiondevices 20A or 20B but includes the two control devices 110A and 110B.

The control device 110A is a control device that controls theto-be-controlled apparatus 30A. The control device 110A generatescontrol data for the to-be-controlled apparatus 30A in the same manneras the control device 10. Then, the control device 110A directlytransmits the control data thus generated to the to-be-controlledapparatus 30A by serial communication via the serial cable CA. Thecontrol device 110B is a control device that controls theto-be-controlled apparatus 30B. Details of the control device 110B arethe same as the details of the control device 110A.

As described above, since the transmission distance of the serial cableCA or the like is relatively short, the control device 110A connected tothe to-be-controlled apparatus 30A via the serial cable CA or the likeneeds to be disposed in the clean room R where a physical distance fromthe to-be-controlled apparatus 30 is relatively short. In other words,it can be said that there are substantial restrictions in that thecontrol devices 110A and 110B, and furniture such as chairs and desks onwhich the control devices 110A and 110B are placed, need to be disposedin the clean room R.

A result of comparison of the configuration of the control system 1illustrated in FIG. 1 with the configuration of the existing controlsystem 100 illustrated in FIG. 2 reveals an advantage that theconfiguration of the control system 1 allows a space occupied by devicesin the clean room R to be reduced. Since there is no restriction thatthe control device 10 must be disposed in the clean room R, the controldevice 10 is disposed outside the clean room R, and the conversiondevices 20A and 20B, which can be defined by hardware smaller than thecontrol device 10 as described above, are disposed in the clean room R.

Note that, when the control devices 110A and 110B of the control system100 preferably are simply integrated into a single control device 10,the single control device 10 must include serial communicationconnectors equal in number to the number of to-be-controlledapparatuses. However, it is not realistic for the single control device10 to include, for example, tens or hundreds of serial communicationconnectors.

Therefore, the control device 10 of the control system 1 is configuredsuch that a function corresponding to one control device 110A or thelike is implemented as one software module and a plurality of thesoftware modules each performing communication data over Ethernet. Thisconfiguration has an advantage that a single control device 10 need notinclude, for example, tens or hundreds of serial communicationconnectors.

A specific configuration example of such a control system 1 will bedescribed in detail below.

FIG. 3 is a block diagram illustrating a first example of a specificconfiguration of the control device 10 according to the presentpreferred embodiment. FIG. 3 illustrates the control device 10, theconversion devices 20A and 20B, and the to-be-controlled apparatuses 30Aand 30B in the control system 1 illustrated in FIG. 1. Further, dashedarrows in FIG. 3 each indicate a control target of a controllers 12A or12B.

As illustrated in FIG. 3, the control device 10 includes the controllers12A and 12B, an operating system (OS) 14, and an Ethernet interface (IF)16.

The controller 12A preferably is a processor implemented as a softwareapplication that performs processing to control the to-be-controlledapparatus 30A. Specifically, the controller 12A generates control datato control the to-be-controlled apparatus 30A, and transmits the controldata thus generated via the OS 14 and the Ethernet IF 16. An address ofthe conversion device 20A is set to a destination address field includedin the control data transmitted by the controller 12A. The controller12A can be implemented via a predetermined program that is executed by aprocessor using a memory or the like.

The controller 12B preferably is a processor implemented as a softwareapplication that performs processing to control the to-be-controlledapparatus 30B. The controller 12B is the same as the controller 12Aexcept that the control target is the to-be-controlled apparatus 30B.

The OS 14 is basic software that runs on hardware of the computerdefining and functioning as the control device 10. The OS 14 is, forexample, Windows (registered trademark) or Linux (registered trademark).

The Ethernet IF 16 is an interface to transmit and receive frames to andfrom the network N, the Ethernet IF 16 conforming to the Ethernetcommunication standard. More specifically, the Ethernet IF 16 includes acommunication circuit that transmits and receives Ethernet frames inaccordance with a communication procedure corresponding to carrier sensemultiple access/collision detection (CSMA/CD) and a connector to which atwisted pair cable used for the Ethernet communication standard such as10/100/1000 BASE-T is connected. The Ethernet IF 16 operates undercontrol of the OS 14.

The conversion devices 20A and 20B perform serial communication with theto-be-controlled apparatuses 30A and 30B, respectively. Further, thecontrollers 12A and 12B perform Ethernet communication with theconversion devices 20A and 20B, respectively.

The control data on the Ethernet communication transmitted by thecontroller 12A via the Ethernet IF 16 is converted into control data inthe serial communication format by the conversion device 20A and is thentransmitted to the to-be-controlled apparatus 30A. The control datatransmitted by the controller 12B is likewise transmitted to theto-be-controlled apparatus 30B.

As described above, in the control system 1, the control device 10, theconversion device 20A, and the like, control each of theto-be-controlled apparatuses 30A and 30B while reducing the maintenancecost of the clean room. Specifically, since there is no restriction thatthe control device 10 must be disposed in the clean room R, a spaceoccupied by devices of the control system 1 in the clean room R is ableto be reduced. Further, a number of computers of the control system 1 isable to be reduced. It is also an advantage that this configuration doesnot need virtualization software (described later).

FIG. 4 is a block diagram illustrating a control device 10A as a secondexample of the specific configuration of the control device 10 accordingto the present preferred embodiment. FIG. 4 illustrates a portioncorresponding to the control device 10 included in the control system 1illustrated in FIG. 1.

As illustrated in FIG. 4, the control device 10A includes controllers12A and 12B, guest OSs 19A and 19B, an Ethernet IF 16, andvirtualization software 18. The control device 10A is capable ofperforming the same functions as the control device 10 illustrated inFIG. 3 has.

The virtualization software 18 is virtualization software that runs onhardware of a computer defining and functioning as the control device10A. The virtualization software 18 can be implemented viavirtualization software running on a host OS, or can be implemented viaa hypervisor running on hardware.

The guest OSs 19A and 19B are each an OS running on the virtualizationsoftware 18, specifically, for example, Windows or Linux. On the guestOSs 19A and 19B, the controllers 12A and 12B run, respectively.

Such a configuration has an advantage that, even when the controllers12A and 12B are implemented via pieces of software running on differentOSs, a single control device 10A is able to control the to-be-controlledapparatuses 30A and 30B.

As described above, in the control system 1, the control device 10A, theconversion device 20A, and the like control each of the to-be-controlledapparatuses 30A and 30B while reducing the maintenance cost of the cleanroom. Specifically, since there is no restriction that the controldevice 10A must be disposed in the clean room R, a space occupied bydevices of the control system 1 in the clean room R is able to bereduced. Further, a number of computers of the control system 1 is ableto be reduced. It is also an advantage that a number of control devicesis able to be reduced in a configuration where controllers implementedvia a plurality of pieces of software running on different OSs areoperated by a single control device.

FIG. 5 is a block diagram illustrating control devices 10B and 10C as athird example of the specific configuration of the control device 10according to the present preferred embodiment. FIG. 5 illustrates aportion corresponding to the main control device M and the controldevice 10 illustrated in FIG. 1.

As illustrated in FIG. 5, the control device 10B includes a controller12A, an OS 14A, and an Ethernet IF 16A. Further, the control device 10Cincludes a controller 12B, an OS 14B, and an Ethernet IF 16B. Thecontrol devices 10B and 10C are connected to the main control device Mvia a network N2.

In such a configuration, the controllers 12A and 12B are implemented viapieces of software running on different control devices. Therefore, thisconfiguration allows a different OS to be used for each of the controldevices. Further, since each of the control devices performs processingon a corresponding to-be-controlled apparatus, processing loads on thecontrol devices 10B and 10C are able to be reduced. It is also anadvantage that a simplified configuration makes it possible to simplifyan operation and enhance fault tolerance.

As described above, in the control system 1, the control device 10A, theconversion device 20A, and the like control each of the to-be-controlledapparatuses 30A and 30B while reducing the maintenance cost of the cleanroom. Specifically, this configuration has an advantage that theprocessing load on each control device is able to be reduced, and thesimplified configuration makes it possible to simplify the operation andenhance the fault tolerance.

FIG. 6 is a block diagram illustrating control devices 10D and 10E as afourth example of the specific configuration of the control device 10according to the present preferred embodiment. FIG. 6 illustrates aportion corresponding to the control device 10, the conversion devices20A and 20B, and the to-be-controlled apparatuses 30A and 30B in thecontrol system 1 illustrated in FIG. 1. Further, dashed arrows in FIG. 6indicate control targets of controllers 12A to 12D.

As illustrated in FIG. 6, the control device 10D includes thecontrollers 12A and 12B, an OS 14A, and an Ethernet IF 16A. Further, thecontrol device 10E includes the controllers 12C and 12D, an OS 14B, andan Ethernet IF 16B. The control devices 10D and 10E are connected to themain control device M via the network N2.

Further, in this configuration, the control system 1 includes fourconversion devices 20A, 20B, 20C and 20D and two switching devices 42Aand 42B.

A destination of control data transmitted by the controller 12A is theconversion device 20A. A destination of control data transmitted by thecontroller 12B is the conversion device 20B. A destination of controldata transmitted by the controller 12C is the conversion device 20C. Adestination of control data transmitted by the controller 12D is theconversion device 20D.

Each of the control device 10D and the control device 10E has the sameconfiguration as the control device 10 illustrated in FIG. 3. Further,the control device 10D and the control device 10E have a redundantconfiguration. That is, the control device 10D and the control device10E are controlled such that one of the control device 10D and thecontrol device 10E serves as an active system and the other serves as astandby system. Like the control device 10 illustrated in FIG. 3, acontrol device defining and functioning as the active system receives acontrol command from the main control device M, and then generates andtransmits control data. A control device defining and functioning as thestandby system does not perform such processing. When a failure occursin the control device defining and functioning as the active system, thecontrol device defining and functioning as the standby system switchesto the active system and operates. Note that, at this time, the controldevice used to serve as the active system may switch to the standbysystem.

The switching device 42A is a switching device disposed on serial cablesconnecting each of the conversion devices 20A and 20C and theto-be-controlled apparatus 30A. The switching device 42A switches signalpaths so that the control data from one of the conversion devices 20Aand 20C reaches the to-be-controlled apparatus 30A, thus the controldata from one of the control devices 10D and 10E defining andfunctioning as the active system is transmitted to the to-be-controlledapparatus 30A.

The switching device 42B is a switching device disposed on serial cablesconnecting each of the conversion devices 20B and 20D and theto-be-controlled apparatus 30B. The switching device 42B performs thesame processing as the switching device 42A does, so that the controldata from one of the control devices 10D and 10E defining andfunctioning as the active system is transmitted to the to-be-controlledapparatus 30B.

In such a configuration, the switching devices 42A and 42B transmits thecontrol data from one of the control devices 10D and 10E defining andfunctioning as the active system to the to-be-controlled apparatuses 30Aand 30B.

As described above, in the control system 1, the control device 10D andthe like, the conversion device 20A and the like control each of theto-be-controlled apparatuses 30A and 30B while reducing the maintenancecost of the clean room. Specifically, since there is no restriction thatthe control devices 10D and 10E are disposed must be disposed in theclean room R, a space occupied by devices of the control system 1 in theclean room R is able to be reduced. It is also an advantage that makinga control device redundant enhances fault tolerance.

Next, a technique relating to control of control data transmissionperformed by the control device 10 will be described.

A transmission speed of the network N is, for example, about 10 to 1000Mbps, and a transmission speed of serial communication is, for example,about 240 to 92160 bps. That is, the transmission speed of the network Nis overwhelmingly higher than the transmission speed of the serialcommunication. Therefore, when control data is transmitted from thecontrol device 10 to the conversion device 20 at a data rate higher thana data rate from the conversion device 20 to the to-be-controlledapparatus 30, the control data is forced to be retained in theconversion device 20. An excessive amount of control data retained inthe conversion device 20 causes a possibility that a buffer willoverflow and may be a factor that increases a delay in arrival of thecontrol data and reduces immediacy of the control. In contrast, anexcessive amount of control data retained causes the buffer to becomeempty and brings about a state in which control data is not transmittedfrom the conversion device 20 to the to-be-controlled apparatus 30.Therefore, a technique to regulate the amount of control data to beretained in the conversion device 20 to an appropriate amount will bedescribed below.

FIG. 7 is a block diagram illustrating details of a functionalconfiguration of the control system 1 according to the present preferredembodiment. In FIG. 7, in addition to the control device 10 and theconversion device 20 included in the control system 1, a functionalconfiguration of the to-be-controlled apparatus 30 is also illustrated;thus, a description of the functional configuration will be alsodescribed below. Here, the control device 10 is installed outside theclean room R, and the conversion device 20 and the to-be-controlledapparatus 30 are installed in the clean room R. Further, theto-be-controlled apparatus 30 includes not only a traveling carrier suchas an overhead traveling vehicle or an unmanned traveling vehicle, butalso a processing device such as a semiconductor manufacturing device.

As illustrated in FIG. 7, the control device 10 includes a controller12, the Ethernet IF 16, and an estimator 54.

The controller 12 is a processor that performs processing to control theto-be-controlled apparatus 30. Specifically, the controller 12 generatescontrol data to control an operation of the to-be-controlled apparatus30, and transmits the control data thus generated via the Ethernet IF16. For example, the controller 12 encapsulates the control data into anIP packet and transmits the IP packet. The address of the conversiondevice 20 is set to the destination address field included in thecontrol data transmitted by the controller 12. The controller 12 can beimplemented via a predetermined program that is executed by a processorusing a memory or the like.

The controller 12 is configured or programmed to include a generator 50and a limiter 52.

The generator 50 is a processor that generates the control data tocontrol the to-be-controlled apparatus 30 and transmits the control datathus generated via the Ethernet IF 16.

The limiter 52 is a processor that limits a transmission data rate ofthe control data to be transmitted by the generator to a rate equal toor less than a predetermined maximum transmission rate. For example, thelimiter 52 may adjust the transmission data rate of the control data tobe transmitted by the generator 50 based on consumption of a buffer 65estimated by the estimator 54. In this configuration, the limiter 52transmits the control data only when the consumption of the buffer 65 issmaller than a threshold Th1, then adjusts the transmission data rate ofthe control data. The threshold Th1 is able to be optionally determinedfrom, for example, values equal to or less than a maximum storagecapacity of the buffer 65 (for example, about 70% to about 80% of themaximum storage capacity). Further, the threshold Th1 may be a valuecorresponding to the transmission speed of serial communication betweenthe conversion device 20 and the to-be-controlled apparatus 30 (forexample, the amount of data carried by serial communication within apredetermined time). The limiter 52 may be implemented via a function ofa device driver of the Ethernet IF 16 or may be implemented viadifferent software. Among the functions of the limiter 52, a function oflimiting the transmission data rate through adjustment based on theconsumption of the buffer 65 estimated as described above is referred toas a first limiter.

Further, in addition to the above operation, when the limiter 52 haspredetermined the maximum transmission rate as a value greater than thetransmission speed of serial communication between the conversion device20 and the to-be-controlled apparatus 30 and then receives a suppressioncommand and a return command (described later) transmitted from theconversion device 20, the limiter 52 may change the maximum transmissionrate in accordance with the commands. Specifically, when receiving thesuppression command from the conversion device 20, the limiter 52 maychange the maximum transmission rate to a value less than a transmissionrate in a normal mode. More specifically, the limiter 52 may set themaximum transmission rate to zero. Further, when receiving the returncommand from the conversion device 20, the limiter 52 may change themaximum transmission rate to a value greater than the transmission speedof serial communication between the conversion device 20 and theto-be-controlled apparatus 30. As described above, this configurationmakes it possible to prevent the buffer 65 of the conversion device 20from overflowing and becoming empty based on the commands transmittedfrom the conversion device 20. Among the functions of the limiter 52, asdescribed above, a function of limiting the transmission data rate basedon the suppression command and the return command is referred to as asecond limiter.

Note that an operation mode of the limiter 52 may be expressed as either“normal mode” or “suppression mode”. The limiter 52 transitions to thesuppression mode when receiving the suppression command and transitionsto the normal mode when receiving the return command in the suppressionmode.

Note that the limiter 52 may enable only one or both of the firstlimiter and the second limiter. When the limiter 52 enables both of thefirst limiter and the second limiter, a lower one of the transmissiondata rate determined by the first limiter and the transmission data ratedetermined by the second limiter is used as the maximum value of thetransmission data rate of the control data to be transmitted by thegenerator 50.

The estimator 54 is a processor that estimates the consumption of thebuffer 65 included in the conversion device 20. There are variousmethods to cause the estimator 54 to estimate the consumption of thebuffer 65. For example, the estimator 54 accumulates transmission dataamounts of the control data transmitted via the limiter 52 and theEthernet IF 16 to estimate the consumption of the buffer 65.Specifically, a point in time at which the consumption of the buffer 65is zero is set as a reference time point, a total amount of the controldata transmitted via the Ethernet IF 16 from the reference time point tothe present time point is set as a data amount D1, a total amount of thecontrol data transmitted by the conversion device 20 to theto-be-controlled apparatus 30 from the reference time point to thepresent time point is set as a data amount D2, and consumption BD of thebuffer 65 is estimated by the following (Equation 1).

BD=D1−D2  (Equation 1)

Note that, in addition to the above method, the estimator 54 may receivenotification of actual consumption of the buffer 65 at the present timepoint or at a past time point ranging from several seconds before toseveral minutes before from an acquirer 66 of the conversion device 20to estimate the consumption of the buffer 65 at the present time point.

The Ethernet IF 16 is an Ethernet IF that communicably connects to thenetwork N. The Ethernet IF 16 is connected to an Ethernet IF 60 of theconversion device 20 via the network N.

Further, the conversion device 20 includes the Ethernet IF 60, a serialIF 62, a converter 64, the acquirer 66, and a transmitter 68.

The Ethernet IF 60 is an Ethernet IF that communicably connects to thenetwork N based on Ethernet. The Ethernet IF 60 is connected to theEthernet IF 16 of the control device 10 via the network N.

The serial IF 62 is a serial communication interface conforming to theserial communication standard (for example, RS-232C, RS-485, or thelike). The serial IF 62 is connected to a serial IF 70 of theto-be-controlled apparatus 30 via a serial cable C.

The converter 64 is a processor that mutually converts communicationdata on Ethernet communication and communication data on serialcommunication. Specifically, the converter 64 receives the control datafrom the control device 10 via the Ethernet IF 60, converts the controldata thus received into the serial communication format, and transmitsthe control data thus converted to the to-be-controlled apparatus 30 viathe serial IF 62. When the control data is encapsulated in an IP packet,the converter 64 first decapsulates the control data and then performsthe conversion. Further, the converter 64 receives the control data fromthe to-be-controlled apparatus 30 via the serial IF 62, converts thecontrol data thus received into the Ethernet communication format, andtransmits the control data thus converted to the control device 10 viathe Ethernet IF 60.

The converter 64 further includes the buffer 65. The buffer 65 is astorage device that temporarily holds the control data received from thecontrol device 10 until the control data is transmitted to theto-be-controlled apparatus 30.

The acquirer 66 is a processor that acquires the consumption of thebuffer 65. The consumption is a data amount of data stored in the buffer65 and may be expressed in units of data amount (for example, [kB] or[MB]) or may be expressed as a percentage of the data amount withrespect to the maximum storage capacity of the buffer 65 (for example,[%]).

The transmitter 68 is a processor that transmits the suppression commandand the return command to the control device 10 based on the consumptionof the buffer 65. Note that the suppression command is also referred toas first information, and the return command is also referred to assecond information.

Specifically, the transmitter 68 transmits the first information (thatis, the suppression command) indicating that the consumption of thebuffer 65 acquired by the acquirer 66 is greater than a first threshold(also referred to as a threshold Th2) to the control device 10. Aftertransmitting the first information, the transmitter 68 transmits thesecond information (that is, the return command) indicating that theconsumption of the buffer 65 acquired by the acquirer 66 is less than asecond threshold (also referred to as a threshold Th3) to the controldevice 10.

Further, the to-be-controlled apparatus 30 includes the serial IF 70 anda main processor 72.

The serial IF 70 is a serial communication interface conforming to theserial communication standard. The serial IF 70 is connected to theserial IF 62 of the conversion device 20 via the serial cable C.

The main processor 72 is an apparatus main processor of theto-be-controlled apparatus 30. For example, when the to-be-controlledapparatus 30 is an apparatus that performs processing on articles, suchas a semiconductor manufacturing facility, a portion corresponding tothe function of performing the processing corresponds to the mainprocessor 72. The main processor 72 operates under control based on thecontrol data received from the control device 10 via the conversiondevice 20.

The processing of the control system 1 described above will be describedbelow.

FIG. 8 is a flowchart illustrating the processing of the control device10 according to the present preferred embodiment. Note that a series ofprocesses illustrated in FIG. 8 is repeatedly executed by the controldevice 10.

In step S101, the estimator 54 estimates the consumption of the buffer65 of the conversion device 20. The estimation of the consumption of thebuffer 65 is performed, for example, by using the above-described(Equation 1).

In step S102, the limiter 52 acquires the consumption of the buffer 65estimated by the estimator 54. Then, the limiter 52 determines whetherthe consumption is less than the threshold Th1 and whether the operationmode is the normal mode. When the limiter 52 determines in step S102that the consumption is less than the threshold Th1 and the operationmode is the normal mode (Yes in step S102), the processing proceeds tostep S103. Otherwise (No in step S102), the processing proceeds to stepS105.

In step S103, the limiter 52 acquires the control data generated by thegenerator 50.

In step S104, the limiter 52 transmits the control data acquired in stepS103 to the conversion device 20 via the Ethernet IF 16. At this time,the limiter 52 limits the data rate of the control data to betransmitted to the conversion device 20 to a rate equal to or less thanthe predetermined maximum transmission rate. The maximum transmissionrate is set to a value greater than the transmission speed of serialcommunication between the conversion device 20 and the to-be-controlledapparatus 30.

In step S105, the limiter 52 suppresses the transmission of the controldata, which in turn suppresses the transmission of the control data tothe conversion device 20 via the Ethernet IF 16.

After step S104 or S105 is executed, the series of processes illustratedin FIG. 8 comes to an end.

FIG. 9 is a flowchart illustrating the processing for changing theoperation mode of the control device 10 according to the presentpreferred embodiment.

In step S201, the limiter 52 determines whether either of thesuppression command and the return command has been received from thetransmitter 68 of the conversion device 20. When either of the commandshas been received, the processing proceeds to step S202. Otherwise, stepS201 is executed again. That is, the limiter 52 waits in step S201 untilreceiving either of the commands from the transmitter 68.

In step S202, the limiter 52 determines whether the command received instep S201 is the suppression command or the return command. When thelimiter 52 determines that the command received in step S201 is thesuppression command, the processing proceeds to step S203. When thelimiter 52 determines that the command thus received is the returncommand, the processing proceeds to step S204.

In step S203, the limiter 52 shifts the operation mode to thesuppression mode.

In step S204, the limiter 52 shifts the operation mode to the normalmode.

Upon completion of the process in step S203 or S204, step S201 isexecuted again.

Through the above-described processing, the operation mode is shiftedbased on the suppression command and the return command received fromthe conversion device 20. Then, the control device 10 limits the dataamount of the control data to be transmitted to the conversion device 20based on estimated consumption of the buffer 65 of the conversion device20, which makes it possible to transmit the control data with the bufferprevented from overflowing and becoming empty.

FIG. 10 is a flowchart illustrating processing of the conversion device20 according to the present preferred embodiment.

In step S301, the acquirer 66 acquires the consumption of the buffer 65.

In step S302, the transmitter 68 determines whether the consumption ofthe buffer 65 acquired by the acquirer 66 in step S301 is greater thanthe threshold Th2. When the transmitter 68 determines that theconsumption of the buffer 65 is greater than the threshold Th2, theprocessing proceeds to step S303. Otherwise, the processing proceeds tostep S311.

In step S303, the transmitter 68 transmits the suppression command tothe control device 10.

In step S311, the transmitter 68 determines whether the consumption isless than the threshold Th3 and whether the operation mode of thecontrol device 10 is the suppression mode. When the consumption is lessthan the threshold Th3 and the operation mode of the control device 10is the suppression mode, the processing proceeds to step S312.Otherwise, the series of processes illustrated in FIG. 10 comes to anend.

In step S312, the transmitter 68 transmits the return command to thecontrol device 10.

Upon completion of the process in step S303 or S312, the series ofprocesses illustrated in FIG. 10 comes to an end.

Note that, in determining whether the operation mode of the controldevice 10 is the suppression mode in step S311, the transmitter 68 mayinquire about the operation mode of the control device 10 in advance andthen acquire the operation mode or may make the determination based onwhether the data amount of the control data received from the controldevice 10 is less than the predetermined threshold.

An operation example of the control system 1 configured as describedabove will be described below.

FIG. 11 is a sequence diagram illustrating the operation example of thecontrol system 1 according to the present preferred embodiment. FIG. 11illustrates a series of processes in which, after starting thetransmission of the control data in the normal mode, the control device10 receives the suppression command and then changes to the suppressionmode to suppress the transmission of the control data. Thereafter, uponreceiving the return command, the control device 10 changes to thenormal mode to resume the transmission of the control data. Further, theconsumption of the buffer 65 at three time points is illustrated ashatched areas in (a), (b) and (c) in FIG. 11. Note that, for the sake ofsimplification, the description of FIG. 11 will be based on the premisethat the unique limitation of the control device 10 (limitation afterstep S102 in FIG. 8) is disabled.

In FIG. 11, it is assumed that the buffer 65 of the conversion device 20is initially empty (refer to (a) in FIG. 11).

In this state, the control device 10 sequentially transmits, to theconversion device 20, pieces of control data D121, D122, and D12 n(denoted as D121 or the like) to control the to-be-controlled apparatus30.

Upon receiving the control data D121 or the like from the control device10, the conversion device 20 converts the control data D121 or the likethus received into the serial communication format and transmits thedata thus converted as control data D231, D232, D233, D234, or the like.

It is assumed that the consumption of the buffer 65 is greater than thethreshold Th2 at the time when the conversion device 20 receives thecontrol data D12 n ((b) in FIG. 11).

Upon the consumption of the buffer 65 becoming larger than the thresholdTh2, the conversion device 20 transmits a suppression command P1 to thecontrol device 10. As a result, the limiter 52 shifts the operation modeto the suppression mode, and suppresses the transmission of the controldata from the control device 10 to the conversion device 20. On theother hand, the control data held in the buffer 65 is uninterruptedlytransmitted to the to-be-controlled apparatus 30, and the consumption ofthe buffer 65 gradually decreases. Then, after transmitting control dataD23 a, the consumption of the buffer 65 becomes less than the thresholdTh3 ((c) in FIG. 11).

Upon the consumption of the buffer 65 becoming less than the thresholdTh3, the conversion device 20 transmits a return command P2 to thecontrol device 10. As a result, the limiter 52 shifts the operation modeto the normal mode, and resumes the transmission of the control datafrom the control device 10 to the conversion device 20, which causespieces of control data D12 a, D12 b, and the like to be transmitted.

As described above, the control device 10 and the conversion device 20transmit the control data to the to-be-controlled apparatus 30 whilepreventing the buffer 65 from overflowing and becoming empty.

Note that the data transmission method of the control device 10described with reference to FIGS. 7 to 11 has an effect of, in aconfiguration where the control device 10 is disposed outside the cleanroom R and the conversion device 20 and the to-be-controlled apparatus30 are disposed in the clean room R, preventing the buffer 65 of theconversion device 20 from overflowing or becoming empty while reducingthe maintenance cost of the clean room. Note that this transmissionmethod is also applicable to a control system unrelated to the cleanroom R. In such a case, the transmission method has an effect ofpreventing the buffer 65 of the conversion device 20 from overflowing orbecoming empty.

As described above, according to the control system of the presentpreferred embodiment, the conversion device is disposed in the cleanroom, which eliminates the restriction that the computer defining andfunctioning as the control device needs to be disposed in the clean roomand allows the control device to be disposed outside the clean room.When a space occupied by the conversion device is smaller than that ofthe control device, a space occupied by the devices of the controlsystem and furniture on which the devices are disposed in the clean roomis able to be reduced, which leads to savings in the space occupied bythe devices in the clean room. As a result, a maintenance cost of theclean room is able to be reduced.

Further, the control device transmits control data to a plurality of theto-be-controlled apparatuses via a plurality of the conversion devicesusing one Ethernet interface. For the control system, the number of thecontrol devices is able to be reduced as compared with a configurationwhere the number of the control devices equals the number of theto-be-controlled apparatuses. Further, a number of interfaces thecontrol device includes is able to be reduced as compared with aconfiguration where the control device includes Ethernet interfaces orlegacy device interfaces (for example, serial communication interfaces)equal in number to the number of the to-be-controlled apparatuses.

Further, the consumption of the buffer of the conversion device isestimated, and the transmission data rate of the control data to betransmitted by the control device is limited in accordance with theestimation. As a result, the control data is able to be delivered to theto-be-controlled apparatus with the buffer of the conversion deviceprevented from overflowing or becoming empty.

Further, when a probability that the buffer will overflow based on theconsumption of the buffer of the conversion device increases, thetransmission data rate of the control data to be transmitted by thecontrol device is reduced even in response to a command from theconversion device, which makes it possible to further reduce theprobability that the buffer will overflow based on respectivedeterminations made by both the devices.

Further, when the probability that the buffer will become empty based onthe consumption of the buffer of the conversion device increases, thetransmission data rate of the control data to be transmitted by thecontrol device is increased, which makes it possible to reduce theprobability that the buffer will become empty.

Although the control systems of the present invention has been describedbased on the preferred embodiments, the present invention is not limitedto the preferred embodiments. Unless deviating from the gist of thepresent invention, a preferred embodiment that results from applyingvarious modifications conceivable by those skilled in the art to thepresent preferred embodiments as well as a preferred embodiment thatresults from combining elements in different preferred embodiments isalso within the scope of the present invention.

Preferred embodiments of the present invention are also applicable to acontrol system that reduces the maintenance cost of a clean room. Morespecifically, preferred embodiments of the present invention areapplicable to a control system or the like to control industrialequipment.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A control system comprising: a to-be-controlledapparatus disposed in a clean room; a control device disposed outsidethe clean room to control the to-be-controlled apparatus throughEthernet communication; and a conversion device disposed in the cleanroom to mutually convert communication data on the Ethernetcommunication with the control device and communication data on serialcommunication with the to-be-controlled apparatus.
 2. The control systemaccording to claim 1, further comprising a plurality of the conversiondevices to perform serial communication with a plurality of theto-be-controlled apparatuses on a one-to-one basis; wherein the controldevice includes one Ethernet interface; and a plurality of controllersperform Ethernet communication with the plurality of conversion devicesvia the one Ethernet interface on a one-to-one basis.
 3. The controlsystem according to claim 1, wherein the conversion device includes abuffer that temporarily holds control data received from the controldevice until the control data is transmitted to the to-be-controlledapparatus; and the control device includes: an estimator that estimatesa consumption of the buffer; a generator that generates the control datato control the to-be-controlled apparatus and transmits the control datawhich is generated; and a first limiter that determines a maximumtransmission rate of the control data based on the consumption estimatedby the estimator and limits a transmission data rate of the control datato be transmitted by the generator to a rate equal to or less than themaximum transmission rate which is determined.
 4. The control systemaccording to claim 2, wherein the conversion device includes: a bufferthat temporarily holds control data received from the control deviceuntil the control data is transmitted to the to-be-controlled apparatus;an acquirer that acquires a consumption of the buffer; and a transmitterthat transmits first information indicating that the consumptionacquired by the acquirer is greater than a first threshold to thecontrol device; the control device includes: a generator that generatesthe control data to control the to-be-controlled apparatus and transmitsthe control data which is generated; and a first limiter that sets amaximum transmission rate of the control data to a value greater than atransmission speed of serial communication between the conversion deviceand the to-be-controlled apparatus, and that changes the maximumtransmission rate to zero upon receiving the first information from thetransmitter.
 5. The control system according to claim 3, wherein theconversion device includes: a buffer that temporarily holds control datareceived from the control device until the control data is transmittedto the to-be-controlled apparatus; an acquirer that acquires consumptionof the buffer; and a transmitter that transmits first informationindicating that the consumption acquired by the acquirer is greater thana first threshold to the control device; the control device includes: asecond limiter that sets a maximum transmission rate of the control datato a value greater than a transmission speed of serial communicationbetween the conversion device and the to-be-controlled apparatus, andthat changes the maximum transmission rate to zero upon receiving thefirst information from the transmitter.
 6. The control system accordingto claim 4, wherein the transmitter transmits, to the control device,second information indicating that the consumption acquired by theacquirer is less than a second threshold after transmitting the firstinformation; and the first limiter changes the maximum transmission rateto a value greater than the transmission speed of serial communicationbetween the conversion device and the to-be-controlled apparatus uponreceiving the second information from the transmitter with the maximumtransmission rate set to zero.
 7. The control system according to claim5, wherein the transmitter transmits, to the control device, secondinformation indicating that the consumption acquired by the acquirer isless than a second threshold after transmitting the first information;and the second limiter changes the maximum transmission rate to a valuegreater than the transmission speed of serial communication between theconversion device and the to-be-controlled apparatus upon receiving thesecond information from the transmitter with the maximum transmissionrate set to zero.
 8. A control device configured to control ato-be-controlled apparatus via conversion between Ethernet communicationand serial communication performed by a conversion device including abuffer that temporarily holds control data received from the controldevice until the control data is transmitted to the to-be-controlledapparatus, the control device comprising: an estimator that estimates aconsumption of the buffer; a generator that generates the control datato control the to-be-controlled apparatus and transmits the control datawhich is generated; and a limiter that determines a maximum transmissionrate of the control data based on the consumption estimated by theestimator and regulates a transmission data rate of the control data tobe transmitted by the generator to a rate equal to or less than themaximum transmission rate which is determined.
 9. A conversion deviceconfigured to mutually convert Ethernet communication performed by acontrol device and serial communication performed by a to-be-controlledapparatus, the conversion device comprising: a buffer that temporarilyholds control data received from the control device until the controldata is transmitted to the to-be-controlled apparatus; and a transmitterthat transmits, to the control device, first information indicating thata consumption of the buffer is greater than a first threshold to changea maximum transmission rate of the control data to be transmitted by thecontrol device to zero.
 10. A method to control a control system thatcauses a control device included in a transfer system to control aconversion device and a to-be-controlled apparatus, the conversiondevice being controlled via Ethernet communication with the controldevice, the to-be-controlled apparatus being controlled via serialcommunication with the conversion device, the method comprising: causingthe control device disposed outside a clean room to control theto-be-controlled apparatus disposed in the clean room via Ethernetcommunication; and causing a conversion device disposed in the cleanroom to mutually convert communication data on Ethernet communicationwith the control device and communication data on serial communicationwith the to-be-controlled apparatus.
 11. A method to control a controldevice that controls a to-be-controlled apparatus via conversion betweenEthernet communication and serial communication performed by aconversion device, the conversion device including a buffer thattemporarily holds control data received from the control device untilthe control data is transmitted to the to-be-controlled apparatus, themethod comprising: estimating a consumption of the buffer; generatingthe control data to control the to-be-controlled apparatus andtransmitting the control data which is generated; and determining amaximum transmission rate of the control data based on the consumptionestimated in the estimating step and regulating a transmission data rateof the control data to be transmitted in the generating step to themaximum transmission rate which is determined.
 12. A method to control aconversion device that mutually converts Ethernet communicationperformed by a control device and serial communication performed by ato-be-controlled apparatus, the method comprising: acquiring aconsumption of a buffer that temporarily holds control data receivedfrom the control device until the control data is transmitted to theto-be-controlled apparatus; and transmitting, to the control device,first information indicating that the consumption is greater than afirst threshold to change a maximum transmission rate of the controldata to be transmitted by the control device to zero.